Downing Street has rejected claims by Russian president Vladimir Putin that there is “nothing criminal” about the prime suspects in the Salisbury nerve agent attack.

The Government said it stood by its assertion that Alexander Petrov and Ruslan Boshirov were officers in Russian military intelligence service the GRU after Mr Putin described them as “civilians”.

Authorities believe the pair smeared the highly toxic chemical Novichok on a door handle at the Wiltshire home of former GRU officer Sergei Skripal, leaving Mr Skripal and his daughter Yulia critically ill.

Responding to Mr Putin’s comments on Wednesday the Prime Minister’s official spokesman reiterated that the men were GRU officers “who used a devastatingly toxic illegal chemical weapon on the streets of our country”.

He added: “We have repeatedly asked Russia to account for what happened in Salisbury in March and they have replied with obfuscation and lies.

“I have seen nothing to suggest that has changed.”

The allegations have already been staunchly denied by the Kremlin and on Wednesday Mr Putin said the men had been discounted as members of his security network.

In an address to the Easter Economic Forum in Vladivostok, he said: “Of course, we looked who these people are. We know who they are, we have found them already.”

He added: “There is nothing special and nothing criminal about it, I’m telling you.”

Questioned on whether the pair were civilians, he replied: “Of course they are civilians.”

Alexander Petrov (left) and Ruslan Boshirov were named as the prime suspects (Metropolitan Police/PA)

The Russian president also expressed the hope Mr Petrov and Mr Boshirov would appear in public to dispel doubt about their true identity.

“I hope that they will emerge (in public) themselves and tell about themselves. It will be better for everyone,” he said on Wednesday.

Television station Russia 24 quoted Mr Petrov as saying he might break his silence next week

Mr Putin’s intervention risks widening the gulf between Russia and the UK over the attempted assassination, which triggered a wave of diplomatic expulsions by both sides.

His hint that the men could soon break their cover recalls memories of the assassination of former KGB agent Alexander Litvinenko on British soil, when suspects Andrey Lugovoy and Dmitry Kovtun publicly rejected the allegations from Russia.